As the next-generation radio communication system for performing higher speed communication with higher capacity, as compared with the 3rd-generation and 3.5th-generation radio communication systems operated at present, an LTE has been standardized by 3GPP, which is a group aiming to standardize a radio communication system. The technical specifications of the LTE have been specified as 3GPP Release 8, and Release 9, which is an upgrade version of Release 8, and an LTE Advanced, which is a sophisticated version of the LTE, have been currently considered.
Furthermore, in the LTE Release 9, detailed functions and requirements of a low power base station (Home eNodeB) have been standardized, which forms a cell (called a small cell) having a small transmission power and being a communication area having a radius in the range from about several [m] to about ten-odd [m] and is a small base station installable in an indoor space. The low power base station is installed in order to distribute traffic of a high power base station (Macro eNodeB), which has transmission power higher than that of the low power base station and forms a cell (a large cell) being a communication area having a radius of about several hundred [m], or to cover a dead zone in the large cell. The configuration of such a radio communication system is called a heterogeneous environment.